1. Field of the Invention
The present invention relates to a process for forming a photographic image using a silver halide light-sensitive material. More particularly, it relates to a process for forming a very contrasty negative photographic image.
2. Description of the Prior Art
A process which comprises adding hydrazine compounds to silver halide photographic emulsions to obtain a photographic characteristic of a contrasty negative image is described in U.S. Pat. No. 2,419,975. This patent discloses that a very contrasty photographic characteristic of a gamma (.gamma.) of more than 10 is obtained when hydrazine compounds are added to silver chlorobromide emulsions and the emulsions are developed using a developer solution having a pH of as high as 12.8. However, a strongly alkaline developer solution having a pH near 13 is unstable because it is easily oxidized by air and, consequently, it cannot be stored or used for a long period of time. Further, development at such a high pH tends to cause fog.
The supercontrasty photographic characteristic of a very high gamma, for either a negative image or a positive image, is very useful for photographic reproduction of halftone images by means of dot images useful for printing plates or reproduction of line drawing images. In the past, for such a purpose, a process which comprises using silver chlorobromide photographic emulsions having a silver chloride content of more than 50 mol % and preferably more than 75 mol % and developing such with a hydroquinone developer solution having a very low effective sulfite ion concentration (generally, a sulfite ion concentration of less than about 0.1 mol/liter) has been used. However, in this process, the developer solution is very unstable because it has a low sulfite ion concentration and, consequently, the developer solution cannot be stored for more than 3 days. Further, since silver chlorobromide emulsions having a comparatively high silver chloride content are used in this process, a high sensitivity cannot be obtained.
Accordingly, the ability to obtain a supercontrasty photographic characteristic useful for reproduction of dot images or line drawings using high speed emulsions and stable developer solutions has been very much desired.
U.S. Pat. No. 3,386,831 describes a process for stabilizing an emulsion by adding a mono-phenylhydrazide of an aliphatic carboxylic acid into an essentially surface-sensitive photographic silver halide emulsion. The object disclosed in U.S. Pat. No. 3,386,831 is to stabilize the emulsion and such differs from the objects of the present invention.